Theoretical modelling of plant hydrological effects on matric suction and slope stability

2019 ◽  
pp. 105-125
Author(s):  
Charles W. W. Ng ◽  
Anthony K. Leung ◽  
Junjun Ni
Keyword(s):  
Slope Stability ◽  
Matric Suction ◽  
Theoretical Modelling ◽  
Hydrological Effects

Modeling the unsaturated soil zone in slope stability analysis

2014 ◽  
Vol 51 (12) ◽  
pp. 1384-1398 ◽  
Author(s):  
L. L. Zhang ◽  
Delwyn G. Fredlund ◽  
Murray D. Fredlund ◽  
G. Ward Wilson
Keyword(s):  
Shear Strength ◽  
Stability Analysis ◽  
Slope Stability ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Matric Suction ◽  
Slope Stability Analysis ◽  
Engineering Practice ◽  
Rate Of Increase ◽  
Nonlinear Shear

The linear form of the extended Mohr–Coulomb shear strength equation uses a [Formula: see text] parameter to quantify the rate of increase in shear strength relative to matric suction. When the [Formula: see text] value is unknown, a [Formula: see text] equal to 15° is sometimes used in the slope stability study to assess the influence of matric suction on the stability of a slope. In many cases, however, a [Formula: see text] value of zero is used, signifying that the effect of matric suction is ignored. Experiment results have shown that the relationship between the shear strength of an unsaturated soil and matric suction is nonlinear. Several semi-empirical estimation equations have been proposed relating the unsaturated shear strength to the soil-water characteristic curve. In this paper, the results of a study using two-dimensional slope stability analysis along with an estimated nonlinear shear strength equations is presented. The effects of using an estimated nonlinear shear strength equation for the unsaturated soils are illustrated using three example problems. Several recommendations are made for engineering practice based on the results of the example problems. If the air-entry value (AEV) of a soil is smaller than 1 kPa, the effect of matric suction on the calculated factor of safety is trivial and the [Formula: see text] value can be assumed to be zero. If the AEV of a soil is between 1 and 20 kPa, the nonlinear equations of unsaturated shear strength should be adopted. For soils with an AEV value between 20 and 200 kPa, an assumed [Formula: see text] value of 15° provides a reasonable estimation of the effects of unsaturated shear strength in most cases. For soils with an AEV greater than 200 kPa, [Formula: see text] can generally be assumed to be equal to the effective angle of internal friction, [Formula: see text], in applications where geotechnical structures have matric suctions around 100 kPa.

scholarly journals Behavior analysis by model slope experiment of artificial rainfall

2015 ◽  
Vol 3 (6) ◽  
pp. 4159-4187
Author(s):  
M. C. Park
Keyword(s):  
Stability Analysis ◽  
Slope Stability ◽  
Pore Water ◽  
Slope Failure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Matric Suction ◽  
Slope Stability Analysis ◽  
Model Slope ◽  
Rainfall Seepage

Abstract. In this study, we performed a model slope experiment with rainfall seepage, and the results were compared and verified with the unsaturated slope stability analysis method. In the model slope experiment, we measured the changes in water content and matric suction due to rainfall seepage, and determined the time at which the slope failure occurred and the shape of the failure. In addition, we compared and verified the changes in the factor of safety and the shape of the failure surface, which was calculated from the unsaturated slope stability analysis with the model experiment. From the results of experiment and analysis, it is concluded that the unsaturated slope stability analysis can be used to accurately analyze and predict rainfall-induced slope failure. It is also concluded that in seepage analysis, setting the initial conditions and boundary conditions is very important. If engineers will use the measured pore water pressure or matric suction, the accuracy of analysis can be enhanced. The real-time monitoring system of pore water pressure or matric suction can be used as a warning of rainfall-induced slope failure.

Hydrological effects of plant on matric suction

2019 ◽  
pp. 17-50
Author(s):  
Charles W. W. Ng ◽  
Anthony K. Leung ◽  
Junjun Ni
Keyword(s):  
Matric Suction ◽  
Hydrological Effects

Analysis of the Influences of Matric Suction of Unsaturated Soil on the Slope Stability

2012 ◽  
Vol 170-173 ◽  
pp. 3186-3189 ◽  
Author(s):  
Li Wang ◽  
Cui Ran Liu
Keyword(s):  
Slope Stability ◽  
Unsaturated Soil ◽  
Yellow River ◽  
Matric Suction ◽  
Saturated Soil ◽  
Equilibrium Method ◽  
Stability Of Slope ◽  
Ultimate Equilibrium ◽  
The Stability ◽  
Test Result

There is suction in unsaturated soil. This is the most obvious difference between unsaturated soil and saturated soil. It is very difficult to measure it, so research has always been done without account of the influences of matric suction of unsaturated soil. In this paper, based on the test result of engineering characteristics of unsaturated soil from Yellow River Embankments, the stability of slope of Yellow River Embankments is analyzed using ultimate equilibrium method and the influencing rule of matric suction on slope is advanced.

The Stability Analyses of Unsaturated Slope Based on the Sarma Method

2011 ◽  
Vol 393-395 ◽  
pp. 1569-1573
Author(s):  
Rong Jian Li ◽  
Qiang Xu ◽  
Wen Zheng ◽  
Hung Chou Lin
Keyword(s):  
Slope Stability ◽  
Unsaturated Soil ◽  
Geotechnical Engineering ◽  
Matric Suction ◽  
Computational Error ◽  
Computational Results ◽  
Soil Slope ◽  
Strength Theory ◽  
Stability Analyses ◽  
The Stability

The study of unsaturated slope stability is one of issues in geotechnical engineering. Firstly, the different treatments of matric suction in the Sarma method are analyzed based on the Bishop’s unsaturated strength theory and Fredlund’s unsaturated strength theory respectively. Then, application of the developed method on the stability analyses of an unsaturated soil slope is also discussed. Through the comparison on the computational results, it still can be concluded that the computational error is slights, which analyzed by means of the developed Sarma method based on the Bishop’s unsaturated strength theory and Fredlund’s unsaturated strength theory.

scholarly journals Bioengineering Solution to Prevent Rainfall-Induced Slope Failures in Tropical Soil

Land ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 299
Author(s):  
Ujwalkumar Dashrath Patil ◽  
Austin J. Shelton III ◽  
Edriel Aquino
Keyword(s):  
Stability Analysis ◽  
Slope Stability ◽  
Water Pressure ◽  
Matric Suction ◽  
Slope Stability Analysis ◽  
Tropical Soil ◽  
Water Retention Curve ◽  
Storm Event ◽  
Storm Events ◽  
Slope Failures

This paper presents test results of comprehensive laboratory and field-testing program efforts for the development of bioengineering solutions such as growing vegetation for protection of slopes from erosion and landslides in a tropical environmental setting. Saturated shear strength of soil was determined using direct shear tests and unsaturated soil properties, such as soil water retention curve (SWRC), were obtained using a computer-controlled hydraulic property analyzer (HYROP) system as well as a WP4C instrument. Climate data were obtained via field instrumentation and appropriate vegetation data were assumed to perform a finite element method-based transient seepage analysis and coupled slope stability analysis to test the potential of tropical hillslope to fail with and without vegetation over a period of one month. Results show that the factor of safety (FOS) for test slope considering case (a) the rainfall and bare ground, case (b) no rainfall with vegetation, and case (c) rainfall with vegetation were found to be 1.630, 1.763, and 1.650, respectively. Although FOS is marginally improved during storm events due to consideration of vegetation as compared to bare slope, this improvement in FOS is much pronounced during antecedent rainfall (i.e., long duration and small intensity) up to the first 26 days of analysis before the storm event (i.e., high intensity and short duration rainfall), which occurs on 27th day and can be instrumental in preventing slope failures. Similarly, the negative pore water pressure (i.e., matric suction) in the top layer is reduced for case (a) from −260 kPa to −40 kPa, increased for case (b) from −260 kPa to −320 kPa, and decreased for case (c) from −260 kPa to −60 kPa. The practical application of these findings is more applicable to the engineered slopes with vegetation during the dry season when the slope is more stable due to high FOS which, however, will need careful watering just to keep them healthy but prevent complete loss of developed matric suction resulting from root water uptake (RWU). In addition, the small improvement in FOS due to matric suction induced from RWU could play a key role in keeping the slope just stable during extreme storm events especially, when FOS of the bare slope is close to 1. To the best knowledge of the authors this is the first documented geotechnical study, using the tropical soil of Guam, which considers the hydro-mechanical effect of RWU-induced matric suction in slope stability analysis in a tropical setting.

scholarly journals Topographic Effects on Three-Dimensional Slope Stability for Fluctuating Water Conditions Using Numerical Analysis

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 615
Author(s):  
Yue Zhou ◽  
Shun-Chao Qi ◽  
Gang Fan ◽  
Ming-Liang Chen ◽  
Jia-Wen Zhou
Keyword(s):  
Slope Stability ◽  
Unsaturated Soils ◽  
Three Dimensional ◽  
Matric Suction ◽  
Surface Shape ◽  
Engineering Practice ◽  
Topographic Effects ◽  
Water Conditions ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

With recent advances in calculation methods, the external factors that affect slope stability, such as water content fluctuations and self-configuration, can be more easily assessed. In this study, a three-dimensional finite element strength reduction method was used to analyze the stability of three-dimensional slopes under fluctuating water conditions. Based on soil parameter variations in engineering practice, the calculation models were established using heterogeneous layers, including a cover layer with inferior properties. An analysis of seepage, deformation and slope stability was carried out with 27 different models, including three different slope gradients and nine different corner angles under five different hydraulic conditions. The failure mechanism has been shown to be closely related to the change in matric suction of unsaturated soils and the geometric slope configuration. Finally, the effect of geometry (surface shape, turning corner and slope gradient) and water (fluctuations) on slope stability are discussed in detail. Emphasis is given to comparing safety factors obtained considering or ignoring matric suction.

scholarly journals Behavior analysis by model slope experiment of artificial rainfall

2016 ◽  
Vol 16 (3) ◽  
pp. 789-800 ◽  
Author(s):  
Min Cheol Park
Keyword(s):  
Stability Analysis ◽  
Slope Stability ◽  
Slope Failure ◽  
Initial Conditions ◽  
Matric Suction ◽  
Slope Stability Analysis ◽  
Seepage Analysis ◽  
Porewater Pressure ◽  
Model Slope ◽  
Rainfall Seepage

Abstract. In this study, we performed a model slope experiment with rainfall seepage, and the results were compared and verified with the unsaturated slope stability analysis method. In the model slope experiment, we measured the changes in water content and matric suction due to rainfall seepage, and determined the time at which the slope failure occurred and the shape of the failure. In addition, we compared and verified the changes in the factor of safety and the shape of the failure surface, which was calculated from the unsaturated slope stability analysis with the model experiment. From the results of experiment and analysis, it is concluded that the unsaturated slope stability analysis can be used to accurately analyze and predict rainfall-induced slope failure. It is also concluded that in seepage analysis, setting the initial conditions and boundary conditions is very important. If engineers will use the measured porewater pressure or matric suction, the accuracy of analysis can be enhanced. The real-time monitoring system of porewater pressure or matric suction can be used as a warning of rainfall-induced slope failure.

Sign in / Sign up

Export Citation Format

Share Document